When you’re shopping around for the best credit cards, you will probably consider one that offers 0% balance transfers if you carry a balance. It could save you big on interest charges. But the problem is that just a few companies issue most of the cards in use in the UK, and if you apply for a card that is allied with one of the companies you already have a card with, you probably won’t get the 0% offer, even if your application for a credit card is approved.

Interest free credit cards are great for people trying to get their debt under control, but card companies use lures like 0% balance transfers to attract new customers, and rarely offer the same rates to existing customers, even if they have outstanding credit histories. There’s no legal reason why they can’t do it, but they don’t do it because they see it as a draw for new customers only.

So if you were to try to get a Mint card and transfer your balance from your NatWest card, you wouldn’t be able to, because both cards are issued by Royal Bank of Scotland. MBNA issues the most different UK credit cards, with nearly 200 brands, while HBOS issues around 50 different cards.